[Bug 1850754] Re: ceph-volume lvm list is O(n^2)

[Launchpad Bug Tracker]

This bug was fixed in the package ceph - 14.2.4-0ubuntu2

---------------
ceph (14.2.4-0ubuntu2) focal; urgency=medium

  [ Dariusz Gadomski ]
  * d/p/issue37490.patch: Cherry pick fix to optimize LVM queries in
    ceph-volume, resolving performance issues in systems under heavy load
    or with large numbers of disks (LP: #1850754).

  [ James Page ]
  * d/p/issue40114.patch: Cherry pick endian fixes to resolve issues
    using Ceph on big-endian architectures such as s390x (LP: #1851290).

 -- Dariusz Gadomski <dariusz.gadomski at canonical.com>  Wed, 06 Nov 2019
11:08:53 +0100

** Changed in: ceph (Ubuntu)
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/1850754

Title:
  ceph-volume lvm list is O(n^2)

Status in Ceph:
  Unknown
Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive queens series:
  New
Status in Ubuntu Cloud Archive rocky series:
  New
Status in Ubuntu Cloud Archive stein series:
  New
Status in Ubuntu Cloud Archive train series:
  New
Status in ceph package in Ubuntu:
  Fix Released
Status in ceph source package in Bionic:
  New
Status in ceph source package in Disco:
  New
Status in ceph source package in Eoan:
  New

Bug description:
  [Impact]
  ceph-volume lvm calls take too much time and the time grows exponentially.
  A simple call may take several minutes depending on the LV configuration.

  [Test Case]
  1. Create a setup with a large number of disks and logical volumes (e.g. 24)
  2. Call ceph-volume lvm list for one of the disks.
  3. Wait for the call to finish.

  [Regression Potential]
  Patch introduces LV caching, so changing LVs while ceph-volume is running may lead to race conditions.

  [Other Info]
  Original bug description:
   
   * Anything else you think is useful to include
   * Anticipate questions from users, SRU, +1 maintenance, security teams and the Technical Board
   * and address these questions in advance

  ceph-volume lvm list calls take very long time due to the fact it has
  been implemented with O(n^2). This leads to unproportionally long
  execution time taking under consideration the fact that no complex
  computation is needed.

  Steps to reproduce:
  1. Create a setup with a large number of disks and logical volumes (e.g. 24)
  2. Call ceph-volume lvm list for one of the disks.
  3. Wait for the call to finish.

  Expected result:
  Call is executed within seconds at most.

  Actual result:
  Call may take even minutes in some circumstances (large number of disks, some OSDs stopped).

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